In the glazing industry the use of multi-paned window lights for use in windows, doors, patio doors and the like has gown tremendously, due to the greater insulative protection that these provide.
However, the problem of thermal bridging is associated with metallic spacer/seal sections.
Efforts to overcome or substantially diminish the thermal bridging effect have included such things as the provision of two metal sections with a thermal break barrier therebetween, such as a urethane layer between the metal sections. While reasonably thermally efficient, such systems are unduly costly, costing in the price range of $1.64 per linear meter of seal length (i.e. $0.50 per linear foot).
Other attempted solutions to the problem have included extruded plastic spacer/seals, and other applied and over-extruded thermoplastic thermal insulators. However, in addition to expense, such spacer/seals are subject to outgassing, which over time can contaminate the enclosed sealed space between the panes, with consequent loss of insulative efficiency and optical clarity.
One solution to the spacer/seal problems, as set forth in my copending U.S. patent application Ser. Nos. 07/609,336, 07/925,537 and 08/081,530, respectively filed Nov. 5, 1990, Aug. 5, 1992 and Jun. 23, 1993 is the use of a hollow cardboard section, wherein utilization is made of the high linear insulative value of cardboard.